PHP Fatal error & Connection Lost

Hello Team,

While Checking My Error Log had seen this error –

PHP Fatal error: Call to a member function get() on null in /public_html/wp-includes/cache.php on line 123

The Second One is – Whenever i am trying to update product am getting message –

Connection lost. Saving has been disabled until you’re reconnected. We’re backing up this post in your browser, just in case

Please have a look at this link https://prnt.sc/kdfbvm

Regards,
Harshad D